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McXtrace - An X-ray ray-trace simulation package

Synchrotron SOLEIL DTU Physics


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McStas: Air

[ Identification | Description | Input parameters | Output parameters | Links ]

The Air Component

Release: McXtrace 1.4 Component simulating atmospheric air.


  • Site:
  • Author: M. B. Nielsen
  • Origin: DTU Fysik, NBI
  • Date: 05.02.2015


The component simulates air and can be inserted as if it was just some extra sample placed somewhere in the beam line.
The air component is intended to be used in all kinds of setups where air may introduce background.
Code structure in this component is based on the component Saxs_spheres.
The shape of the sample may be a filled box with dimensions
xwidth, yheight, zdepth, a filled cylinder with dimensions radius and yheight,
a filled sphere with radius R.
(NB: As we assume air to be an ideal gas, the volume fractions of the elements in the gas are merely the mole fractional part of the given element.
From this the number density of atoms/molecules is calculated)
The air is dry and assumed to be made of nitrogen, oxygen and argon - all other constituents are neglected.

So far the calculations of the scattering probability (and hence also the weight multiplier) assumes the x-ray source to be unpolarized.
Further the component does not yet account for absorption of x-rays. I.e. absorption is simply omitted, but it may OR may NOT be negligible.
I have not yet looked into this last question, so I can't say if the lack of absorption is a bad thing or if it is allowable.

COMPONENT air1 = Air(
frac = 0.4, pressure = 50000, temperature = 270,
xwidth = 0.5, yheight = 0.5, zdepth = 1.5, target_index = 1,
focus_xw = 0.5, focus_yh = 0.5)
AT (0, 0, 15) RELATIVE Origin

Input parameters

Parameters in boldface are required; the others are optional.
fracfraction of rays to scatter from the air [ ]0.3
pressuretotal pressure of the air gas [Pa]101325
temperatureabsolute temperature [K]273.15+21.1
xwidthmWidth of the air volume.0
yheightmHeight of the air volume.0
zdepthmDepth of the air volume.0
radiusmRadius of spherical or cylindrical air volume.0
target_xmX-coordinate of sampling window.0
target_ymY-coordinate of sampling window.0
target_zmZ-coordinate of sampling window.6
target_index index of target component putting sampling window on a subsequent component.0
focus_xwmWidth of the sampling window.0
focus_yhmHeight of the sampling window.0
focus_awradHorizontal (width) opening angle of sampling window.0
focus_ahradVertical (height) opening angle of sampling window.0
focus_rradRadius of circular sampling window.0

Output parameters

Parameters in boldface are required; the others are optional.


[ Identification | Description | Input parameters | Output parameters | Links ]

Generated on 2022-02-07 20:46:44

Last Modified: Wednesday, 11-May-2022 22:46:12 CEST
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